Just learning Photoshop: Eraser and background eraser won't work when I'm in the midst of editing in Photoshop, but if I save the image as a jpg then I can use eraser. Is there something wrong with my Photoshop settings or something I'm not doing right? I have version CS 5 Extended 12.1 x64. Any help greatly appreciated.
The Eraser Tool essentially paints background color pixels if you're working on the Background layer, but if you have actual layers in your document then it will introduce transparency. Those are two pretty different things.